DE3025590A1 - CIRCUIT ARRANGEMENT FOR A TELECOMMUNICATION SYSTEM - Google Patents

Description

P.H. Rees 20-2

The invention relates to a circuit arrangement for a Telephone exchange of the type mentioned in the preamble of claim 1. This circuit arrangement is for modular construction intended.

The use of modular construction in the design of telephone exchanges is so advantageous because it eliminates the problems of expanding the PBX simplified when the number of participants and connecting lines increases during the lifetime of the switch. Another aspect of modular construction is that that modules can be used in telephone exchanges which are somewhat different from the telephone exchange for which these modules are actually designed had been. A telephone exchange can then, for example, by adding more modern versions of the originally used modules can be expanded.

The object of the invention is to provide a circuit arrangement for a telephone exchange as described in the preamble of claim 1 specified type in which a modular extension of the telephone system in a simple manner is possible.

This object is achieved according to the invention by the measures characterized in claim 1. With such a Telephone exchanges can create various sizes of local exchanges with a single design will; also, a small or medium-sized local switch can easily become a large local switch be expanded. In terms of structure, the pern

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intercom system according to the invention preferably from two or more levels or switching network groups, each having a central part, hereinafter referred to as a directional switching unit designated; becomes, and one or more subscriber switching units exhibit. These switching network groups are arranged so that they can be used in a unified telephone system work together. In this respect the telephone exchange according to the invention differs of known, modular telephone switching systems.

In order to switch a subscriber through to a connection line, a voice connection is established via a directional coupling unit and each subscriber switch established using only one directional switch, even if the subscriber and the connection line belong to different switching network groups. Similarly, a Indoor or local connection, i.e. a connection between two to the same switching system or switching network group connected subscriber lines, only via a directional coupling unit guided. The use of only one directional coupling unit when establishing the connection is economical with regard to the capacity of the coupling units and, above all, the occupancy of the processor in the control device.

The various coupling units are for signal and control information connected by signal paths that are separated from the speech paths, with the necessary information as regular messages using the message transmission system is transmitted in the coupling units. If the speech paths and the signaling paths are time division multiplexed channels these different paths can be formed by different time channels on the same bus.

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The basic principle of such a signaling is that no coupling unit has any prerequisite with regard to the internal operations of another coupling unit. Therefore, the internal messages are purely functional Art. When using such a signaling philosophy The switching network groups do not need to be designed in the same way, i.e. they can come from different generations of development and use different processors. Therefore, an existing telephone exchange

lü by a new switching network group of a more modern type than the one already existing switching network groups can be expanded. Furthermore, the direction switching units and the subscriber switching units not in the same place; the directional coupling units do not need to be in the same place either be.

The invention will now be explained in more detail using an exemplary embodiment. Figures 1 and 2 show a simplified one Block diagram of a switching system with two coupling network groups. Fig. 1 shows some between the coupling units and signal paths running between the switching network groups, while FIG. 2 shows some between the switching units and represents speech paths running between the switching network groups. Both types of trails are actually present and separate from each other functionally separated, but if the switching system works fully digitally in the time division multiplex process, then the two types of route can go through the same physical route be educated.

In Figures 1 and 2, each switching network group has one Directional coupling unit DSUl, DSU2 and one or more line coupling units (or concentrator modules) on, of which the line coupling unit LUSl to the coupling network group

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belongs, which has the directional coupling unit DSUl, and of which the subscriber coupling unit LSUx to which the directional coupling unit DSU2 having switching network group belongs. Each directional coupling unit, hereinafter referred to as DSU for short, contains, inter alia, a switching network DSS, which can be designed in one or more stages depending on the traffic, a control circuit CCE and a signaling device MTS. A subscriber coupling unit, hereinafter referred to as LSU, also has a switching network CS, which can again be designed in one or more stages, a signaling device MTS and a Control circuit LCE. Each LSU also has subscriber line circuits like LC for serving the subscriber lines, and each DSU is with a number of incoming and outgoing trunk lines as shown in FIG. The signaling paths also include paths to other exchanges (see Fig. 1) and are from the trunk speech paths functionally separated.

Fig. 1 shows part of the network of signaling paths between the coupling units and also some of the signaling paths to other switching systems VSTx, VSTy, while Figure 2 similarly shows some speech paths. Both in terms of the signaling path and also with regard to the speech path, each LSU has access to each DSU, and each DSU has signaling connections to

2b "of every other DSU. Furthermore, every DSU has access to every other DSU via corresponding speech paths, these paths being provided for through connections is transmitted using the pulse code modulation method and the signaling is also carried out digitally on the collective channel Äbe: · ¹ that from several groups

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existing K ppelne according to the invention.:.; is also in analog working distribution systems, although it is there ■ is less beneficial.

Each DSU belongs to a special billet network group and ü can be in relation to the one or more LSU of this switching network group and to the TtJ 11 subscriber lines connected to this LSU referred to as mother rDSU; will. The parent DSU manages its dependent LSU and stores it centrally Data that are subscribers connected to this LSU are permanently assigned. However, the parent DSU does not set up all connections for its subscriber lines as it does later will be explained in more detail.

In the LSU, as they are present in the exemplary embodiment, there are eight PCM busbars from the switching matrix CS, so that with the compulsion that each LSU-DSU connection uses at least two PCM bus lines for security reasons, the switching system can have up to four switching network groups. If more than four switching network groups are provided, are larger CS switching matrices with more than eight PCM collecting lines necessary. The arrangement of the LSU-DSU collecting lines can be flexible, according to the above mentioned need, two such busses between one LSU and one DSU to be provided.

As can be seen from the figures, the DSU are also among each other connected by means of PCM trunk lines to provide both voice and signal connections between to enable the switching network groups. These connections between the switching network groups are used for double coupling, i.e. used for through connections. For security reasons, there are at least two PCM manifolds between provided for each pair of DSUs. These "inter" ~ DSU collection

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Lines can also, apart from through-connections, used for overflow connections when traffic is heavy will.

Pig. 1 shows that each LSU and each DSU has signaling facilities MTS has, for the signaling between an LSU and a DSU or between a DSU and a LSU and for signaling between each pair of DSUs. These signaling interconnections are on PCM manifolds, usually on the time slot l6. For security reasons, every signaling device has MTS two lying on different PCM collecting lines Intermediate signaling lines. Use the intermediate signaling lines belonging to a collective channel thus the same physical paths in the switching network as the voice links.

There are three types of speech path connections:

a) a participant is connected to another participant,

b) a participant is connected to a connection line,

c) a connecting line is with another connecting line tied together.

In case a) only one DSU is involved in establishing the connection, and this DSU can, but need not be, the parent DSU of the calling party. In case b) there is only one DSU with involved in connection establishment, but in this case the DSU associated with the trunk is involved.

Finally, in case c), two DSUs are involved if the two connecting lines are not connected to the same DSU and then only this DSU is involved. Therefore, the double coupling is only necessary for through connections if the Intermediate lines between the DSU cannot be used for overflow connections.

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As already mentioned, for all normal internal connections, outgoing originating connections and incoming End connections only used one DSU, so that essentially all connection establishment and connection initiation processes can be processed by a DSU. With a normal indoor connection, each DSU can be used for central traffic processing can be selected, while the two types of Connection establishment with the participation of a connection line that DSU is used to which the connection line is used line is connected. For through connections, however, two DSUs are used when both trunk lines are not connected to the same DSU. The through connection is treated as two half connections, each from of the associated DSU.

The DSU assigned to the calling line has the task of free and busy status for all original connections to check the connection, to bring its memory up to date accordingly and saved, sini-permanent Output data that provide information about the authorization class of this caller. These functions are in the In the event of a termination, carried out by the DSU of the called party. In the case of an incoming or outgoing one Link is the DSU assigned to the trunk responsible for all data on this connection line.

It follows from the above arrangement that the control circuit a DSU is designed so that two such control circuits in different switching network groups on the same Connection can be involved and that these two control circuits send each other regular messages can.

The following are the different types of binding

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described in more detail, although other connection establishment methods are conceivable, but those described are the preferred ones.

From the following description it will be seen that for all connections except for through connections the Established connection is made only by one directional coupling unit, resulting in an economical arrangement of the Telephone exchange leads.

in this case the DSU assigned to the incoming trunk Van directs all main operations of the connection setup; it is therefore called the master DSU. It recognizes the incoming occupancy, works together with the previous switching system and ensures that the data stored on the connection line is brought up to date. It also sends the commands relating to the establishment and release of the connection from the LSU assigned to the called subscriber. May This routing DSU wrong with the assigned to the called subscriber DSU 'the same DSU be) inform su to the control circuit, that an incoming connection request to that line is present, and to the status information to obtain this line. The mother DSU of the called line brings the data for the subscriber up to date and works as a "watchdog" for the connection for security reasons, so that it can initiate auxiliary operations to protect the line in the event of incorrect operation of the master DSU. However, the mother DSU does not take part in the establishment or release of the connection if it is not also the DSU of the incoming connection.

jjO is management. The master DSU monitors the connection during of the conversation and carries out the necessary work.

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The control circuit of the master DSU analyzes the desired Phone number and may also use the identity the incoming connection line and uses this information to determine whether a through connection or an end connection is present. In the latter case, it is given a position number and the master DSU sends an occupancy request message to the DSU assigned to the called line. This message contains the required position number and a Connection identifier.

The DSU assigned to the called line, i.e. the mother DSU, checks the called line for its idle status and marks it as occupied in the case of being free. In the case of a telephone extension group, this parent DSU is included a search in this extension group to select a free circuit and an "absolute" position number obtain. The mother DSU also makes the data information of the called line, for example the authorization class, accessible that / required for normal connection establishment is. The parent DSU then sends an occupancy feedback for the incoming connection to the master DSU. These The message contains the status information of the called line and, in the case of a telephone extension group, the "absolute" position number. This message also includes a connection identifier.

If the response indicates that the connection can be established, the master DSU sends a seizure request message, which contains the desired position number to the LSU of the called line. This LSU sends an occupancy feedback to the master DSU to accept the connection. The lead DSU and the LSU will then connect in the normal way. The master DSU monitors the connection during the call

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and carries out the necessary work, for example the recall of a register.

The master DSU and LSU monitor the connection for on incoming disconnection signal or a signal from the called subscriber that indicates the hanging up of the handset and work directly together on disconnection and trip monitoring. After triggering, the Leit-DSU a release request message to the DSU of the called Line that contains the line's position number so that this DSU now marks the line as free.

The master DSU also keeps all dynamic records of the connection, such as those for billing necessary for the duration of the connection and forwards this information if necessary. Which concerns this connection The transmission of data usually takes place at the end of the connection establishment phase and / or held at the end of the call to keep the message traffic between the DSU low keep.

If the incoming trunk and the called trunk belong to the same switching network group, only one is DSU is involved, and the various messages then go directly to the programs concerned in order to run these programs to bring to execution, instead of these messages running through the signaling devices MTS.

^

In this case, the master DSU is the one to be used Connection line Vab is assigned. The caller's mother DSU, however, analyzes those received by the caller Dialing digits. Therefore, the caller's LSU operates at the beginning

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with its mother DSU until the latter has activated the DSU to which the connecting lines (Yab) for the appropriate remote connection are connected. Thereafter, the control DSU communicates directly with the LSU assigned to the caller in order to establish and release the connection.

The DSU assigned to the calling party brings the data assigned to the calling party up to date and is at the beginning active, since it uses the call number analysis to determine the identifiers for the master DSU and the outgoing connection line

lü makes. The mother DSU then no longer actively accepts participates in the establishment of the connection when it has passed the connection to the master DSU, but it is working for security reasons as a "watchdog" for the connection in order to be able to initiate relief measures if necessary. The lead DSU communicates with the nearest switching system, monitors the connection during the call and makes the necessary calls Working out.

The LSU detects that the caller's handset has been lifted and receives his dialing digits. When noting when the handset is picked up, the LSU sends an occupancy message, containing the position number of the caller to the parent DSU. This DSU queries its memory for the caller's idle status and marks it when the idle status is determined the calling party as busy. The master DSU then sends a die

2 ^l j Request to send a message containing dialing digits to the LSU, which contains the position number of the caller and which is considered to be the initial acceptance of the call. The LSU waits until it receives η dialing digits from the caller, with η dialing digits being sufficient to identify an outgoing connection and its direction. The choice is limited in time. The LSU then sends these η dialing digits in a block to the mother DSU. Initial zeros, as in code 01 for the

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London local area or in code u2 ',' 9 for: · the ürtsoereich Harlow, are sent to the Le it-DSU, except not all parts of the η dialing digits are counted. In the last ivall de is: · Fourth, of η equal to three, to make provision for transmitter connections and fUc for the code digits of long-distance connections.

The LCU assigned to the caller analyzes the received Dial digits and, if necessary, ask for additional dial digits to determine whether the connection is an end connection or is an outgoing connection. In the last! ■ '"■ it starts the Identifiers of the outgoing direction and the associated DSU. The calling party's mother DSU now sends a seizure request message , a connection identifier, the identifier of the outgoing trunk and all the received dialing digits, to the Leiu-Doll.

l ^l j) Upon receipt of this occupancy request message, the control DSU searches for a free connection line in the desired direction and then sends an acceptance message to the caller's mother DSU after a successful search. The control DSU now brings its memory up to date by marking the selected connection line there as busy. If it does not find a connection line free, it sends a message which returns the connection to the LSU, which either returns a busy signal to the caller or tries to establish an alternative route.

When the master DSJ has found a suitable connection line and when it has accepted the connection, it takes over the connection. The mother DSU then has no one: another Share in further connection establishment. The master DSU works immediately to establish the connection together with the LSU of the calling party. Zuerci, she sends one

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Routing message to the LSU with the instruction that the DSU for the connection is responsible '".; then it demands that Rest of the dialed number ·. This guidance message contains the position numerals of the calling party. On receipt of this · position number the LoU sends the remainder of the call number to the DSiJ. The DSU is now working with the LSU to establish the connection together, operates with the following intermediary system and sends the relevant information, for example the sign indicating that the called subscriber lifts the handset to the LSU.

The master DSU holds the connection as with an end connection The relevant dynamic memory values are available for further use (billing).

If the calling party and the dialed connection lines come from the same coupling network group, the situation is the same as with an incoming end connection.

Indoor connection

In this case, any DSU can be chosen for the connection, e.g. to balance the traffic load. The first Part of the connection establishment is the same as for an outgoing originating connection, while the last part is the same as for an incoming end connection starts up. The speech path thus runs via the caller's LSU, the selected DSU and the LSU of the called party, so that depending on the position of the calling and called subscriber line, up to three DSUs will call may be involved in establishing the connection.

When the caller determines that the handset has been lifted, the LSU sends an occupancy message with the position number of the caller to the LSU's mother DSU. The mother DSU

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checks your memory for the caller's price status and marks the caller as busy there when the idle status is determined. The parent DSU then sends messages to the Request for dialing digits as with an outgoing original connection return. The caller's mother DSU analyzes the dialing digits and requests additional dialing digits from the LSU. she determines the type of connection and, if there is an internal connection, receives the position number called. This DSU determines which DSU is to be the master DSU (see the section with the analysis of the call number).

After completion of the call number analysis and after determination the identifier of the master DSU and the position number called the mother DSU of the calling party sends an occupancy request message, the desired position number and a connection identifier contains, to the master DSU. If the master DSU can handle the call, it sends an Feedback to the caller's DSU to take responsibility for the connection. The Leit-DSU works for the rest of the connection establishment with the LSU of the caller together, with their first action being the transmission of a routing message to the caller's LSU, which informs this LSU that it is the master DSU.

The master DSU sends a seizure message to the DSU of the desired line as in the case of an incoming end connection.

The DSU of the desired line carries out suitable work and sends a response to the master DSU, which includes the relevant class of service and status information with the "absolute" position number in the case of a connection to a group of extensions. The master DSU now proceeds to the connection establishment phase continues, works with the calling party’s LSU and the called party's LSU to find the appropriate To switch through speech channels.

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This master DSU is for connection monitoring and the Triggering as with the other described connections is responsible.

Depending on the affiliation of the calling and called line to the same switching network group and the selection One, two or three switching network groups are involved in an algorithm used by a master DSU. This shouldn't be internal Affect operations of the control circuits because only the transmission of the messages by the destination DSU is influenced: this follows from that in the control circuits Separate processing carried out by CCE.

The through connection is treated as two half connections, where the DSU for the incoming trunk Vda is the master DSU for the incoming half-connection and the main party for the whole connection, while the DSU for the outgoing connection Vdb is responsible for the outgoing connection. The incoming half-connection is basically same as the first part of an incoming end connection, and the outgoing half connection runs like that second part of an outgoing original connection. If the two connecting lines Vda, Vdb are in different Coupling network groups are located twice. If, on the other hand, they are in the same switching network group, finds no double coupling takes place.

The control circuit CCE of the DSU of the incoming trunk Vda needs to know whether the trunks belong to the same switching network group because if they are, the Control circuit CCE during the establishment of the outgoing half-connection the functions of switching through and tripping

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the through connection must suppress. Apart from this suppression, the internal operations of the control circuit CCE is unaffected by whether the "connecting lines are in the same switching network group or in different switching network groups. The control circuit of the incoming Master DSU begins with the connection handling and analyzes the desired one from the previous switching system received call number, possibly using the identifier of the incoming connection line. From it the DSU determines whether the connection is an end connection or an outgoing connection, i.e. a through connection, is. In the latter case, the DSU also receives the identifier of the outgoing connection line and the identifier of the outgoing one Head DSU.

After the call number analysis is finished, the incoming Leit-DSU an occupancy request message for the outgoing Master DSU, which contains the identifier of the outgoing trunk and all dialing digits received from the incoming DSU contains. When the outgoing master DSU receives this message, it selects a connection line in the desired direction and at this point checks whether it is also the incoming DSU or not. If it is assumed that the trunks belong to different switching network groups, set the outgoing DSU establishes a cross connection from the selected connection line to an intermediate line that runs between two switching network groups. It then sends a message to the incoming master DSU containing the identifier of the selected link receives. If the trunks are in the same switching network group, the outgoing part needs the DSU

j5O no cross line; the DSU sends, in this case a message to the incoming part of the DSU, which contains the identifier of the selected outgoing trunk.

The incoming control DSU now switches a voice connection

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from the incoming connection line to the intermediate line or to the outgoing connection line.

The incoming master DSU is for traffic with the previous one Switching system and for updating the storage content relating to the incoming connection line responsible, while the outgoing master DSU is responsible for the traffic with the subsequent switching system and is responsible for updating the memory content relating to the outgoing connection. If an intermediate line is used between the switching network groups, each DSU updates the memory contents on the assigned End of this intermediate line. In the meantime, the incoming master DSU is still receiving dial digits from the previous one Switching system and it stores this. Requested in the appropriate connection establishment phase the incoming DSU these dialing digits, which the incoming DSU incorporates in messages between the DSU and thus to the outgoing DSU broadcasts. This DSU then sends the remainder of the dialing digits of the call number to the subsequent switching system.

All other signaling information that either the incoming DSU from the preceding switching system or received by the outgoing DSU is analyzed for receipt of a message between the DSU, if necessary is sent to the other DSU.

ΘΓ1

Alternative connecting belts may be required for through connections his and possibly also door outgoing source connections.

In the case of a through connection, that of the incoming one works

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Connection line associated DSU as well as incoming master DSU as well as the main DSU. If it determines the outgoing direction in a first election, the DSU that has this Direction is assigned, select a free connection line. However, if this DSU does not have a frefe trunk in the can find the desired direction, for this reason it sends a message back to the Xeit-DSU and rejects the connection return. The DSU assigned to the desired direction deletes all used, dynamic memory contents and doesn't care about the connection. The master DSU now offers the connection in a second dial of another DSU, which is intended for the outgoing direction. This third DSU now checks whether there is one in the desired direction Connection line is free. Operations continue in this manner until the connection is found to be cannot be established. Receives in this pail the subscriber receives a busy signal.

The mode of operation for an originating connection is basically the same as for a through connection: the The caller's master DSU initially assumes responsibility for the connection that it offers to the DSU that the first choice direction is assigned. This DSU accepts the connection if it finds a suitable outgoing trunk or it rejects the connection if she cannot find a free connection line. In the latter case, the caller's DSU offers the connection to another DSU for a second choice direction, etc.

The above assumes that a direction is defined so that each direction is specific to a switching network group but there can be multiple directions for the same destination. For example, several Directions, i.e. several trunk sets, lead to a main area center (one direction from each DSU).

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Claims (1)

Oipl.-Phys »Leo Thul Stuttgart F.H. Rees 20-2 INTERNATIONAL STANDARD ELECTRIC CORPORATION, NEW YORK Claim "1. Circuit arrangement for a telephone exchange with subscriber coupling units, each of which has a number Subscriber lines are assigned and each have their own control circuit, with directional coupling units, to which incoming and outgoing connection lines are connected, which directional coupling units furthermore each have their own control circuit and each have one or more subscriber coupling units are assigned, and with intermediate lines that the subscriber switching units with the directional switching units connect such that each subscriber coupling unit Has access to every directional coupling unit, since ^ h ^ ge ^ kemz ^ e ^ chne ^ t that to establish a connection between two subscriber lines (Tl, Tz) connected to the telephone exchange, the one subscriber line (Tl) serving subscriber coupling unit (LSUl) via an intermediate line with a directional coupling unit (DSUl, DSU2) and this via another intermediate line with the one serving the other subscriber line (Tz) Subscriber coupling unit (LSUx) is connected, this connection under the control of this directional coupling unit belonging control circuit (CCE) is established that for the establishment of an incoming connection the with direction connected to the incoming connection line (van) -2- 130018/0605 P.H. Rees 20-2 connection unit (DSU) via a further link with a subscriber coupling unit serving the called line (LSU) is connected, this connection under the control of this directional coupling unit associated control circuit (CCE) is established, and that to establish an outgoing connection the the subscriber coupling unit (LSU) serving the calling line via a further intermediate line with an access to a outgoing connecting line (Vab) having directional coupling unit leading in the desired direction (DSU), this connection being under the control of the control circuit associated with this directional coupling unit (CCE). 2. Circuit arrangement according to claim 1, dadu.ggh ^ .gekennzejahrigt ;, that the information relating to a subscriber line, such as their authorization class and their free or occupied state, in the memory of the directional coupling unit for that belonging control device is stored, the line coupling unit serving this subscriber line is assigned, and that when this subscriber line is involved in a connection, the information via this subscriber line in the memory with regard to the new status of this subscriber line and the out the memory for the purpose of establishing and / or controlling the connection to the latest information Stand is brought. 3. Circuit arrangement according to claim 2, dadijrc ^ ggkgjin ^ eich ^ net that the directional switching unit in which the data of a line are stored, all connections of this line monitored regardless of whether the connection is established via this line by this directional coupling unit has taken place or not, and that in the event that the - 3- 130018/0605 F.H. Rees 20-2 Directional coupling unit establishing the connection works incorrectly, one of the lines involved in the connection assigned directional coupling unit takes over the connection establishment. k . Circuit arrangement according to Claim 2 or Claim 3, da ^ d_u ^ h ^ gjke ^ nje _< ichjnet_, that in the case in which a connection is to be established between two lines which are served by the switching system and the subscriber switching units belonging to different direction switching units are connected, the connection establishment is initiated by the control circuit of that directional coupling unit that belongs to the subscriber coupling unit of the caller, and that at the time when the dialing information of the caller identifies the subscriber coupling unit belonging to the called line, one of the directional coupling units is selected for further control of the connection establishment is, preferably according to traffic considerations. 5 »Circuit arrangement according to one of claims 1 to k, §3§3 ££ ^ SB} iS ^} ^ B ^ S ^ BS-i. ' that the intermediate lines between the coupling units have speech wires and signal wires, with speech and signal wires being functionally separated. 6. Circuit arrangement according to claim '-, dadjarch ^ Sekennae ^ ch ^ act, that further, au = Spi ecliadern formed and used for through connections interconnects each connect a pair of directional coupling units with each other and that in the production of a through connection between two connecting lines connected to the same directional coupling unit this directional coupling unit takes over the entire connection establishment. -k- 1 3001 8/0605 BAD ORlQlNAl F.H. Rees 20-2 7. Circuit arrangement according to claim β, netj that further intermediate lines formed from signal cores also connect a pair of directional coupling units to one another. 8. Circuit arrangement according to claims 5 * 6 or 7 »da ^ marked by ^ that the connections in the time division multiplex under message transmission by means of pulse code modulation and that various Channels on the same time division multiplexed trunk for communication over the speech path and the signal path to be used. 9. Circuit arrangement according to one of claims 1 to 8, in which switching network groups each consist of one or more Line coupling units, a directional coupling unit and intermediate lines formed between these coupling units are, da ^ UT ^ i ^ eJce ^ njjej ^ chriet ,, that the switching network groups are connected by intermediate lines running between the corresponding coupling units and that for Extension of the switching system one or more switching network groups can be added, with the addition of additional Intermediate lines between the existing and added switching network groups. -D- 13001 8/0605